Distribution Of Fish Larvae Research Articles

Late winter larval fish assemblage in the southern East China Sea, with emphasis on spatial relations between mesopelagic and commercial pelagic fish larvae

We examined larval fish assemblages in the southern East China Sea during late winter where large spawning grounds of several commercial pelagic fishes are formed. Our samples include a total of 187 species or taxa of larval fish belonging to 118 genera, 96 families, and 18 orders. Mesopelagic fish larvae, mainly Stomiiformes, Aulopiformes, and Myctophiformes, accounted for 66.5% of the total catch, while commercial species such as Trachurus japonicus, Scomber spp., and Trichiurus japonicus for 16.6%. Based on the species composition, three assemblages were recognized: Kuroshio (KUR), Shelf-Break (BRE), and Shelf (SHE) assemblages. KUR assemblage was mainly characterized by various mesopelagic fishes such as Sigmops gracilis, Diaphus spp., and Myctophum asperum, BRE assemblage by both commercial pelagic and mesopelagic species, SHE assemblage by demersal species such as Lepidotrigla spp. and Gobiidae spp. Both abundance and diversity were highest in KUR assemblage, although food availability for the larvae would be poorest. The combination of variables of sea surface temperature-chlorophyll a concentrations best explained the larval distribution. Except for Benthosema pterotum, the center of distribution of mesopelagic fish larvae was clearly separated from that of the commercial species by the Kuroshio front. However, a northward intrusion of the Kuroshio transported mesopelagic fish larvae onto the shelf, forming the BRE assemblage. Competition for prey between mesopelagic and commercial pelagic fish larvae would potentially occur if the intrusion is strong.

Vertical distribution and migration of fish larvae in the NW Iberian upwelling system during the winter mixing period: implications for cross‐shelf distribution

AbstractThe vertical distribution and vertical migrations of fish larvae and implications for their cross‐shelf distribution were investigated in the northern limit of the NE Atlantic upwelling region during the late winter mixing period of 2012. The average positive values of the upwelling index for February and March of this year were far from normal, although the average hydrographic conditions during the period of study were of downwelling and the water column was completely mixed. Fish larvae, most in the preflexion stage, were concentrated in the upper layers of the water column and their distribution was depth stratified, both day and night. However, the larval fish community was not structured in the vertical plane and fish larvae did not show significant diel vertical migration (DVM), although five species showed ontogenetic vertical migration. In regions of coastal upwelling and in the absence of DVM, the location of fish larvae in the water column is crucial for their cross‐shelf distribution. Thus, the cross‐shelf distribution of the six most abundant species collected in this study can be explained by the surface onshore flow associated with coastal downwelling, retaining larvae of the coastal spawning species with a relatively shallow distribution in the shelf region and transporting larvae of slope spawning species onto the shelf. The wide vertical distribution shown by larvae of the offshore spawning species could be an adaptation of these species to ensure that some larvae reach the inshore nursery areas.

The impact of environmental variability on Atlantic mackerel Scomber scombrus larval abundance to the west of the British Isles

The value of the Continuous Plankton Recorder (CPR) fish larvae dataset, with its extensive spatio-temporal coverage, has been recently demonstrated with studies on long-term changes over decadal scales in the abundance and distribution of fish larvae in relation to physical and biological factors in the North Sea. We used a similar approach in the west and southwest area of the UK shelf and applied a principal component analysis (PCA) using 7 biotic and abiotic parameters, combined with Hierarchical Cluster Analysis (HCA), to investigate the impact of environmental changes in the west and southwest area of the UK shelf on mackerel larvae during the period 1960–2004. The analysis revealed 3 main periods of time (1960–1968; 1969–1994; 1995–2004) reflecting 3 different ecosystem states. The results suggest a transition from an ecosystem characterized by low temperature, high salinity, high abundances of zooplankton and the larger phytoplankton groups, to a system characterized by higher temperature, lower salinities, lower abundances of zooplankton and larger phytoplankton and higher abundances of the small phytoplankton species. Analysis revealed a very weak positive correlation between the Second principal component and mackerel larvae yearly abundance, attributed to the North Atlantic Oscillation (NAO). The results presented here are in broad accord with recent investigations that link climatic variability and dynamics of mackerel reproduction. However, the growing body of literature that documents statistical correlations between environment and mackerel needs to be supplemented by local process studies, to gain more insight and to be able to predict mackerel response to climate change scenarios. Utilising the strength of the CPR dataset, namely its unique temporal coverage, in an analysis where other data (such as egg surveys) are drawn in to compensate for the spatial issues could prove to be the way forward.

Distribution of fish larvae on the Vitória-Trindade Chain, southwestern Atlantic

This work presents a checklist of ichthyoplankton collected along the Vitória-Trindade chain with oblique bongo hauls to a depth of 20 m in the summer and in the winter. Larvae were classified according the adult habitat as reef, epipelagic or mesopelagic. The variables season, depth, sampling time, environment type and distance from the continental shelf were used to test the correlation with the larval density of each larval category. In the summer, 3,897 larvae were captured (identified at the family, genera or species level, n = 44, 33 and 82, respectively) and 1,026 larvae were captured in the winter (19, 17 and 25, respectively). Only the variables season and environment type significantly affected density, with their influence varying among larval categories.

Ecological distribution of fish larvae and juveniles in the Yangtze River estuary and its adjacent waters in spring

Ecological distribution of fish larvae and juveniles in the Yangtze River estuary and its adjacent waters in spring

The importance of a conservation unit in a subtropical basin for fish spawning and growth

Studies for location of breeding sites and early development areas of freshwater fish in subtropical basins are still incipient. Most of the existing knowledge is based on sampling in environments impacted by dams of hydroelectric power plants and studies in areas with characteristics similar to the original are lacking. In this way, this study evaluated the spatial distribution of the ichthyoplankton in a Conservation Unit (Turvo State Park, Rio Grande do Sul State, Brazil) on the subtropical basin of the Uruguay River, in a stretch with no hydroelectric power plants and at best preservation condition. The density distribution of fish eggs and larvae was evaluated quantitatively through plankton nets samples, while the analysis of the species composition of larvae was assessed qualitatively through plankton nets and light traps sampling. There were significant differences in two stretches situated inside the park separated by a waterfall, both in the distribution of eggs and larvae and in species composition of the larval assemblage. Our results indicate that periods without the total flood of Yucuma Falls influences the composition of the ichthyoplankton and the existence of two distinct reproductive environments over an approximate length of 50 km. This result supports the hypothesis that in subtropical basins the alternation of flood and dry periods can influence the structure of fish community and evidences the importance of maintenance of hydrological conditions to fish reproduction in this river section, because showed the importance of the habitat diversity in the river channel to fish recruitment.

Diel variation in the vertical distribution of fish larvae forced by upwelling filaments off Punta Angamos (northern Chile)

The role of daily vertical migration (DVM) of ichthyoplanktonic associations off Punta Angamos, in northern Chile, was examined. In September 1998 and January 1999, two oceanographic surveys were conducted during coastal upwelling events. Fish larvae were collected during the day/night in three depth strata (0-20, 20-80 and 80-200 m) and inside/outside of upwelling filaments. The study area was dominated by a southward flow along 200 m depth; meanwhile, the Ekman layer did not exceed 20 m depth. The greatest accumulation of larvae was found in the middle layer (20-80 m), where the current velocity was low and did not interact with the circulation associated with upwelling the filament formation. Most fish larvae were found in non-upwelling waters in the middle stratum. Independent of the origin of water (upwelling/non-upwelling), larvae of Dioge-nichthys laternatus (Myctophidae), Engraulis ringens (Engraulidae) and Bathylagus nigrigenys (Bathylagidae) showed a deeper vertical distribution during the day, suggesting a daily vertical migration. This behavior can potentially increase retention of larvae near the coast in productive areas through vertical evasion of the Ekman layer during upwelling events.

Patterns in larval fish assemblages under the influence of the Brazil current

The present work investigates the composition of larval fish assemblages in the area under the influence of the Brazil Current (BC) off the Southeastern Brazilian Bight. Ichthyoplankton was sampled during two oceanographic cruises (November–December/1997 – spring; May/2001 – autumn) with bongo nets oblique tows. Seasonal variation and a coastal-ocean pattern in the distribution of larval fish was observed and was influenced by the dynamics of the water masses, Coastal Water (CW), Tropical Water (TW) and South Atlantic Central Water (SACW), the last two of which were transported by the BC. During spring, the shelf assemblage was dominated by larvae of small pelagic fishes, such as Sardinella brasiliensis, Engraulis anchoita and Trachurus lathami, and was associated with the enrichment of shallow water by the SACW upwelling. In autumn, the abundance of coastal species larvae was reduced, and the shelf assemblage was dominated by Bregmaceros cantori. A transitional assemblage occurred during the spring, and comprised mesopelagic and coastal species. In both seasons, the oceanic assemblage was dominated by the mesopelagic families, Myctophidae, Sternopthychidae and Phosichthyidae. The oceanographic conditions also demonstrated clear differences between the northern and southern subareas, particularly in the shelf zone. This was especially the case during autumn when a latitudinal gradient in larval fish assemblages became more pronounced.

Unravelling the Gordian knot! Key processes impacting overwintering larval survival and growth: A North Sea herring case study

Unraveling the key processes affecting marine fish recruitment will ultimately require a combination of field, laboratory and modelling studies. We combined analyzes of long-term (30-year) field data on larval fish abundance, distribution and length, and biophysical model simulations of different levels of complexity to identify processes impacting the survival and growth of autumn- and winter-spawned Atlantic herring (Clupea harengus) larvae. Field survey data revealed interannual changes in intensity of utilization of the five major spawning grounds (Orkney/Shetland, Buchan, Banks north, Banks south, and Downs) as well as spatio-temporal variability in the length and abundance of overwintered larvae. The mean length of larvae captured in post-winter surveys was negatively correlated to the proportion of larvae from the southern-most (Downs) winter-spawning component. Furthermore, the mean length of larvae originating from all spawning components has decreased since 1990 suggesting ecosystem-wide changes impacting larval growth potential, most likely due to changes in prey fields. A simple biophysical model assuming temperature-dependent growth and constant mortality underestimated larval growth rates suggesting that larval mortality rates steeply declined with increasing size and/or age during winter as no match with field data could be obtained. In contrast better agreement was found between observed and modelled post-winter abundance for larvae originating from four spawning components when a more complex, physiological-based foraging and growth model was employed using a suite of potential prey field and size-based mortality scenarios. Nonetheless, agreement between field and model-derived estimates was poor for larvae originating from the winter-spawned Downs component. In North Sea herring, the dominant processes impacting larval growth and survival appear to have shifted in time and space highlighting how environmental forcing, ecosystem state and other factors can form a Gordian knot of marine fish recruitment processes. We highlight gaps in process knowledge and recommend specific field, laboratory and modelling studies which, in our opinion, are most likely to unravel the dominant processes and advance predictive capacity of the environmental regulation of recruitment in autumn and winter-spawned fishes in temperate areas such as herring in the North Sea.

Patterns in Larval Fish Diversity, Abundance, and Distribution in Temperate South African Estuaries

Estuaries are important nursery areas for fishes worldwide but large-scale studies of spatial patterns of use are lacking. This study presents data on larval fish diversity, abundance and distribution within and among a range of temperate estuary types, spanning 25 systems sampled from 1998 to 2008 in South Africa. A standardized boat-based plankton towing technique was used. Estuary type and physico-chemical conditions played a defining role in the trends observed. Estuary resident Clupeidae and Gobiidae dominated the mid-channel larval catch, particularly the preflexion stages in permanently and intermittently open estuaries and in estuarine lakes. Permanently open estuaries were also characterized by high numbers of larvae and early juveniles of marine migrant fishes. Density was higher in warmer months (spring and summer), which coincides with peak spawning in coastal habitats coupled with zooplankton maxima in the warm-temperate region. A strong seasonal component was also evident in larval fish catches in cool-temperate systems, but this peak coincided with late winter rainfall. River inflow provides a strong influence on food availability and larval survival. Species richness and diversity was higher in estuaries with either extensive habitat variability and/or a strong, natural good supply of river flow. This was particularly evident in the higher numbers of marine migrant larvae in these systems. Freshwater deprived estuaries also displayed high species diversity due to the higher incidence of marine straggler species. Characterization of salinity into zones provided a valuable means to understand distribution and abundance dynamics. Mesohaline zones had the highest density of larval fishes, providing ideal food patches. A select suite of species dominate the larval fish assemblages in the various estuary types studied. These patterns persist but species abundance and rank may vary interannually based on productivity and larval fish survival.

Importance of Reservoir Tributaries to Spawning of Migratory Fish in the Upper Paraná River

AbstractRegulation of rivers by dams transforms previously lotic reaches above the dam into lentic ones and limits or prevents longitudinal connectivity, which impairs access to suitable habitats for the reproduction of many migratory fish species. Frequently, unregulated tributaries can provide important habitat heterogeneity to a regulated river and may mitigate the influence of impoundments on the mainstem river. We evaluated the importance of tributaries to spawning of migratory fish species over three spawning seasons, by comparing several abiotic conditions and larval fish distributions in four rivers that are tributaries to an impounded reach of the Upper Paraná River, Brazil. Our study confirmed reproduction of at least 8 long‐distance migrators, likely nine, out of a total of 19 occurring in the Upper Paraná River. Total larval densities and percentage species composition differed among tributaries, but the differences were not consistent among spawning seasons and unexpectedly were not strongly related to annual differences in temperature and hydrology. We hypothesize that under present conditions, densities of larvae of migratory species may be better related to efficiency of fish passage facilities than to temperature and hydrology. Our study indicates that adult fish are finding suitable habitat for spawning in tributaries, fish eggs are developing into larvae, and larvae are finding suitable rearing space in lagoons adjacent to the tributaries. Our findings also suggest the need for establishment of protected areas in unregulated and lightly regulated tributaries to preserve essential spawning and nursery habitats. Copyright © 2014 John Wiley & Sons, Ltd.

Large-Scale Ichthyoplankton and Water Mass Distribution along the South Brazil Shelf

Ichthyoplankton is an essential component of pelagic ecosystems, and environmental factors play an important role in determining its distribution. We have investigated simultaneous latitudinal and cross-shelf gradients in ichthyoplankton abundance to test the hypothesis that the large-scale distribution of fish larvae in the South Brazil Shelf is associated with water mass composition. Vertical plankton tows were collected between 21°27′ and 34°51′S at 107 stations, in austral late spring and early summer seasons. Samples were taken with a conical-cylindrical plankton net from the depth of chlorophyll maxima to the surface in deep stations, or from 10 m from the bottom to the surface in shallow waters. Salinity and temperature were obtained with a CTD/rosette system, which provided seawater for chlorophyll-a and nutrient concentrations. The influence of water mass on larval fish species was studied using Indicator Species Analysis, whereas environmental effects on the distribution of larval fish species were analyzed by Distance-based Redundancy Analysis. Larval fish species were associated with specific water masses: in the north, Sardinella brasiliensis was found in Shelf Water; whereas in the south, Engraulis anchoita inhabited the Plata Plume Water. At the slope, Tropical Water was characterized by the bristlemouth Cyclothone acclinidens. The concurrent analysis showed the importance of both cross-shelf and latitudinal gradients on the large-scale distribution of larval fish species. Our findings reveal that ichthyoplankton composition and large-scale spatial distribution are determined by water mass composition in both latitudinal and cross-shelf gradients.

Larval fish distribution and retention in the Canary Current system during the weak upwelling season

AbstractThe spatial distribution of fish larvae was studied in the Canaries‐African Coastal Transition Zone, outside the strong upwelling season. An onshore–offshore transition in the larval fish community structure was observed, from a coastal assemblage dominated by small pelagics (sardine, anchovy, mackerel), bounded by the upwelling front, to an offshore assemblage dominated by mesopelagic species (mainly Myctophidae, Phosichthydae, Gonostomatidae). Distribution of the neritic larvae was deeply influenced by the intense mesoscale activity found in the area, both horizontally (larvae were advected offshore but were always retained within the upwelling area) and vertically (larvae were deepened in the vicinity of two anticyclonic eddies). A combined effect of the upwelling front and a cyclonic–anticyclonic eddy dipole is likely the successful retention mechanism for these larvae. These results support the current belief that retention may be higher than previously thought in upwelling areas. Oceanic larvae were also collected in higher abundances near the front and an anticyclonic eddy. Neritic and oceanic larvae frequently showed a differentiated position in the water column, although they sometimes coexisted. Finally, larval connectivity between Islands within the Canary archipelago is suggested. The present study thus contributes to the understanding of the complex dispersal and retention processes in the Canaries‐African Coastal Transition Zone. However, results also highlight the poor knowledge of this region compared with the other three main Eastern Boundary Upwelling Systems in terms of ichthyoplankton dynamics. The importance of routine monitoring programs of commercial and non‐commercial species in the area is emphasized.

<b> Temporal distribution of ichthyoplankton in the Forquilha river, upper Uruguay river – Brazil: Relationship with environmental factors </b> - doi: 10.4025/actascibiolsci.v36i1.17993

This study aimed to evaluate the temporal distribution of fish eggs and larvae in the Forquilha river (upper Uruguay river/Brazil) and its relationship with environmental variables. Ichthyoplankton and abiotic factors were sampled from September 2006 to August 2007. At the laboratory, samples were sorted and larvae were identified to the lowest possible taxonomic level. For data analysis we applied One-way Anova, Tukey’s test, Pearson correlation and PCA. In this study 200 eggs and 308 larvae were collected, showing differences in the temporal distribution and influence of abiotic factors. Larvae were identified in all stages of development, being distributed in three order and eight families. These results point that the lower portion of the Forquilha river is an important drift and nursery area for fish larvae of the upper Uruguay river. The breeding season for most species was greatly marked, between October and January, coinciding with the increase in temperature and decrease of the water flow. The response of reproductive intensity varies according to the environmental variables.

Fish larvae at fronts: Horizontal and vertical distributions of gadoid fish larvae across a frontal zone at the Norwegian Trench

The reproduction and early life history of many fish species are linked to the physical and biological characteristics of fronts. In order to ascertain linkages between frontal physics and fish larvae, we investigated distributional differences among gadoid fish larvae comparing these to both horizontal and vertical variability in hydrography and abundances of potential copepod prey The investigation was carried out at a frontal zone along the Norwegian Trench in the northern North Sea, and was based on a series of cross-bathymetric sampling transects. Tows with a large ring net and an opening–closing net were used for describing fish larval horizontal and vertical distributions, while a submersible pump was used for describing vertical distributions of copepods. Hydrographic profiles and current velocity measurements were used to outline variability in temperature, salinity and current structure. Measurements demonstrated a distinct bottom front at the southern slope of the Trench with deepening isopycnals and high chlorphyll a concentrations. Abundances of both gadoid fish larvae and copepods peaked in vicinity of the front around mid-depth, and findings points to an inter-connection between the vertical and horizontal distributions of each species. However, the three-dimensional pattern of distribution differed significantly among species of larvae and species of copepods. The study underlines the complexity of bio-physical interrelationships in the frontal zone, and indicates that the zone encompasses specific ecological niches to which each species of fish larvae is adapted.

Are the Laurentian Great Lakes great enough for Hjort?

Abstract Hjort's insights on marine fish recruitment and larval fish advection are presumed not applicable to freshwater lakes because most freshwater lakes are small. The Laurentian Great Lakes (LGL), however, are large enough for certain oceanic-type hydrodynamics, such as strong currents and upwelling, to affect the distribution and survival of larval fish and thus fall under Hjort's purview. However, there are evolutionary constraints because LGL species underwent an evolutionary bottleneck during glaciation, ∼10 000 years BP. We consider three narratives pertinent to both the spatial scale and the evolutionary time-scale of the LGL. The first reviews recent evidence of offshore advection and subsequent cross-lake dispersal of larval and juvenile yellow perch, a coastal demersal species in Lake Michigan. The second narrative suggests that biotic interactions, rather than spatial scale itself, could account for the transition in the critical period of Lake Michigan yellow perch period from a juvenile to a larval critical period. In the third narrative, we consider whether the deep LGL lack a significant native pelagic larval fish predator. We propose that the LGL, in combination with the older World's Great Lakes, present an opportunity to explore evolution and adaptation of fish to oceanic type physical conditions.

Larval fish distribution and their relationship with environmental factors in the southern Tyrrhenian Sea (central Mediterranean) during two years of sampling

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Ocean–estuarine connection for ichthyoplankton through the inlet channel of a temperate choked coastal lagoon (Argentina)

We examined the fish larvae colonising pattern of the Mar Chiquita lagoon (Argentina). We hypothesised that in this microtidal lagoon, winds could regulate fish larvae dynamics. Ichthyoplankton samples were taken in marine waters, the surf zone and the estuary. Previous studies showed no reproduction by fishes with planktonic eggs inside the lagoon. However high abundance of eggs and larvae of Brevoortia aurea collected within the estuary also suggest possible spawning activity. Throughout the study period, the cumulated richness of fish larvae was slightly higher in the estuary. However, univariate analysis revealed a higher number of species per tow in marine waters than in the estuary. The lowest average values of fish density, number of species and diversity recorded in the surf zone suggest that this area is only used as a transient corridor between the sea and the lagoon. The canonical correspondence analysis (CCA) indicated that wind direction, tidal stage, temperature and rainfall contributed significantly to the fish larvae distribution patterns observed; being ‘onshore wind’ the most important variable affecting fishes. Our results show how winds, in addition to pushing seawater into the lagoon, contribute to larvae recruitment into this estuary. Finally, we discuss the role of small lagoons in the life-history of coastal fishes.

SUMMER ASSEMBLAGES OF ICHTHYOPLANKTON IN THE WATERS OF THE EAST CHINA SEA SHELF AND AROUND TAIWAN IN 2007

This study investigated the relationships between assemblages of larval fish and hydrographic features in the East China Sea (ECS) and seas surrounding Taiwan during the summer of 2007. A survey was conducted from 2007 July 1 to 2007 July 11 in the ECS and from 2007 July 4 to 2007 July 16 in the waters surrounding Taiwan. A total of 12,670 larval fishes belonging to 95 families, 163 genes, and 189 species were identified. Engraulis japonicus and Sillago japonica were the 2 dominant species, accounting for 56.15% and 6.66% of the fish larvae samples. The cluster analysis results showed that the fish larval distribution patterns corresponded to hydrographic conditions. The results were also used to identify the following larval assemblages: the Kuroshio assemblage, coastal assemblage, Changjiang diluted water (CDW) / Yellow Sea mixed water assemblage, and Taiwan Strait water assemblage. The spatial distribution results showed a clear association between high abundances of larval fishes and shallow water areas near the ECS coast, and between low abundances and offshore Kuroshio water. The canonical correlation analysis results indicated that abundances of E. japonicus and S. japonica were strongly and positively correlated with chlorophyll a, but negatively correlated with salinity. These associations suggest that food sources and CDW might be crucial factors that determine the abundance and distribution of larval fishes during the summer.

Diel-depth distributions of fish larvae off the Balearic Islands (western Mediterranean) under two environmental scenarios

The diel vertical distribution of fish larvae off the Balearic Islands during late autumn and summer was analysed in relation to the environmental conditions. Four fixed sampling stations, located in the outer shelf and slope zones, were sampled during both the day and night by means of oblique hauls at different water depths. In autumn the first 60m were characterised by vertical mixing and relatively higher fluorescence values, while summer was characterised by strong near-surface stratification and the presence of a Deep Fluorescence Maximum (DFM). The fish larval community was dominated by mesopelagic species, myctophiforms and stomiiforms, with some differences in species composition and their relative contribution between periods. A higher number of species was observed to reproduce in summer. The diel vertical distribution patterns differed among species and, within species, some differences were detected between the day and night. Although their relative depth preferences were similar between surveys, seasonal comparisons for the most abundant species showed that in autumn larvae presented both a shallower distribution during the day and a deeper distribution during the night than in the summer period. The larvae of all species, except for Argyropelecus hemigymnus, were absent from layers below 200m. In these deeper layers, only A. hemigymnus larvae and juvenile stages of myctophiforms and stomiiforms were found. Another group of species, including Hygophum benoiti, Ceratoscopelus maderensis, Cyclothone braueri and Lampanyctus crocodilus, characterised the surface assemblage, mainly appearing in the first 50m during the day, while at night their distribution was wider, extending to deeper layers. Benthosema glaciale, Symbolophorus veranyi and Myctophum punctatum were located at intermediate levels (mostly 50–100m). Larval size stratification was evident for the most abundant species, with younger stages being found at shallower depths in the water column, while postflexion stages presented a wide distribution at night, undergoing vertical displacement to the near-surface layers during the day. The roles of the position of the thermocline, the availability of food and light intensity as factors modulating these differences are discussed.